If $8.0 \ g$ of a radioactive isotope has a half-life of $10 \ hrs$. The half-life of $2.0 \ g$ of the same substance is ...... $hrs$.

What is the half-life period of a nucleus in $days$ if at the end of $4.2$ $days$,$N = 0.798 \ N_0$?

If the half-life of a substance is $5 \, \text{years}$,then the total amount of substance left after $15 \, \text{years}$,when the initial amount is $64 \, \text{grams}$,is ....... $\text{gm}$.

$A$ radioactive substance has a half-life $(t_{1/2})$ of $60 \ minutes$. After $3 \ hours$,what percentage of the radioactive substance will remain?

If $1 \ \mu g$ of radium $(^{226}Ra)$ has disintegrated for $500$ years,how many alpha particles will be emitted per second?

The half-life of $1 \ g$ of a radioactive sample is $9 \ hours$. The radioactive decay obeys first-order kinetics. The time required for the original sample to reduce to $0.2 \ g$ is .......... $hours$.